Are PCBS in phytoplankton and zooplankton at equilibrium with the water in which they live?

Abstract

Food chain bioaccumulation of polychlorinated biphenyls (PCBs) can result in harmful concentrations within higher trophic level organisms such as fish and humans. It is important to consider how the concentrations of PCBs in phytoplankton and zooplankton affect higher trophic organisms. It was hypothesized that polychlorinated biphenyl (PCB) concentrations within primary producers such as phytoplankton simply reflect chemical equilibrium of PCB congeners freely dissolved in the water column and in the lipid fraction of the plankton. In this study, the freely dissolved PCBs in the water of Lake Cochituate, MA, were measured using polyethylene (PE) passive sampling strips, thereby avoiding problems associated with colloid-bound PCBs. Phytoplankton and zooplankton samples were measured to determine their PCB levels and lipid fractions. The phytoplankton were at equilibrium in the fall of 2016. The phytoplankton and zooplankton appeared close to equilibrium in the spring of 2017. The large PCB congeners measured in the spring of 2017 may have been undersaturated, consistent with the idea that rapid growth leads to phytoplankton undersaturation.